There are a number of different medicament delivery devices that have been developed with the aim to provide self-administration to the users. In that respect the medicament delivery devices should be easy to use, i.e. not requiring a lot of learning or reading of instruction manuals. Further, the medicament delivery devices should be easy to use regarding ease of preparing the device for drug delivery even for patients with reduced dexterity of their hands.
One step that often is required in order to have the medicament delivery device ready for medicament delivery is to attach a delivery member to the front end of the medicament delivery device. A common design of a delivery member is a pen needle for pen-type injectors. Generally the pen needles have a threaded hub that can be screwed onto and off the pen injector. When screwing onto the injector, the rear end of the needle penetrates an elastic membrane or septum of a medicament container in order to provide a passage from the container through the needle.
For some patients this screwing action can be quite difficult, especially for persons with reduced dexterity of their hands and/or persons with shaking hands that are difficult to control. These patients may not be able to attach a needle by a screwing action in order to receive a dose of medicament. Document WO 2008/008694 discloses one attempt for facilitating the attachment of a pen needle. The front end of a cartridge holder collet is arranged with a number of resilient fingers having protrusions on their outer surfaces. When a pen needle is to be attached it is pushed onto the resilient fingers whereby the internal threads of the needle engage with the protrusions of the fingers. In order to lock the engagement the collet is then pushed axially onto the neck of a medicament container, which presses the fingers against the hub of the pen needle. For removing the pen needle from the collet, the medicament container is pushed back again, whereby the fingers may be pressed inwards by the user, which releases the pen needle so that it may be dropped in a suitable safety container.
Even though it might be reasonably easy to put the pen needle onto the collet, it requires further handling in that the medicament container has to be pushed in position in order to lock the pen needle to the collet. There is a risk for patients with reduced functions of their hands or patients with uncontrolled shaking of hands that the needle falls off before the medicament container has been pushed forward in the locking position. Also, many patients are used to the screwing action both for attaching and in particular detaching the pen needle, which is not provided for with the device according to WO 2008/008694.